Currently, light-emitting diodes (LEDs) are widely used in a backlight module for a liquid crystal display. The quantity of the light-emitting diodes is decreased to reduce the manufacture cost of the liquid crystal display, thus resulting in a larger gap between two adjacent LEDs. Therefore, the optical design and assembling precision of the backlight module are more and more challenging. One of the key factors is to precisely align the LEDs in the vertical direction of the backlight module.
Nowadays, the LEDs are fixed on a printed circuit board (PCB) of a light bar with the surface mounting technology (SMT). First, a solder paste is printed on the soldering pads of the printed circuit board. Second, the LEDs are placed on the soldering pads having the solder paste. Finally, the LEDs are fixed on the soldering pads by heating with a reflow furnace. However, even through the LEDs can be precisely placed on the soldering pads initially, yet portions of the signal lines connected and adjacent to the soldering pads are exposed without being covered by the solder mask layer of the PCB, the molten solder will be easily distributed fully on the exposed areas due to its surface tension property, thus causing the LEDs to be deviated from the original adhering positions on the soldering pads, also affecting the alignment precision of the LEDs in the vertical direction of the backlight module.
Therefore, there is a need to improve the alignment position of the LEDs in the vertical direction of the backlight module.